High-entropy superparaelectrics with locally diverse ferroic distortion for high-capacitive energy storage

Superparaelectrics are considered promising candidate materials for achieving superior energy storage capabilities. However, due to the complicated local structural design, simultaneously achieving high recoverable energy density (Wrec) and energy storage efficiency (η) under high electric fields remains a challenge in bulk superparaelectrics. Here, we propose utilizing entropy engineering to disrupt long-range ferroic orders into local polymorphic distortion disorder with multiple BO6 tilt types and diverse heterogeneous polarization configurations. This strategy reduces the switching barriers, thereby facilitating the emergence of superparaelectric behaviors with ideal polarization forms. Furthermore, it enables high polarization response, negligible remnant polarization, delayed polarization saturation, and enhanced breakdown electric fields (Eb) in high-entropy superparaelectrics. Consequently, an extraordinary Wrec of 15.48 J cm–3 and an ultrahigh η of 90.02% are achieved at a high Eb of 710 kV cm–1, surpassing the comprehensive energy storage performance of previously reported bulk superparaelectrics. This work demonstrates that entropy engineering is a viable strategy for designing high-performance superparaelectrics.

Editorial Note: Parts of this Peer Review File have been redacted as indicated to remove third-party material where no permission to publish could be obtained.

REVIEWER COMMENTS
Reviewer #1 (Remarks to the Author): This manuscript reports on high-entropy SPEs with remarkable energy storage performance achieved through local structural design.The authors propose a strategy to design ideal SPEs using entropy engineering to tailor local polarization.A suite of micro-characterization techniques has been employed to reveal local polymorphic distortion with diverse BO6 tilt types and heterogeneous polarization configurations brought on by high entropy effects, analyzing their positive impact on the SPE characteristics and energy storage performance.The manuscript provides a rigorous and in-depth analysis of the correlation between local structures and performance.From the perspectives of energy storage performance and novelty, it indeed holds substantial appeal and significance for the field of dielectrics.Therefore, I think this manuscript can be accepted after addressing the following comments: 1.The design of local multi-phase symmetry is intriguing.Please elaborate on the advantages of this design over the common coexistence of the R and T phases in BNBT.In addition, what is the effect of distorted oxygen octahedra on energy storage performance?2. For the designed composition of (1 -x)BNBT-xSLTT, why did the authors choose SLTT as the dopant?Besides improving the entropy of the BNBT material, are there any other reasons?3.While in-depth exploration of the temperature stability of energy storage performance has been conducted, frequency stability is equally crucial for practical applications.Therefore, I suggest adding dielectric performance tests related to frequency in order to corroborate the frequency stability of the energy storage performance.4. For the large Eb of 710 kV/cm obtained in the SLTT-0.30sample, authors consider the high Eb is associated with entropy-induced lattice distortion, ultrafine grains (Ga), clear and dense grain boundaries, wide bandgaps (Eg), and ultralow dielectric loss (tanδ).Which factor may play a major role?Can you further explain? 5. Some minor issues: (1) The four typical vibrational modes in Raman spectra should be indicated in Supplementary Fig. 3. (2) The authors should present the configuration entropy of all the components at appropriate places to help the reader understand the relationship between SLTT and configuration entropy.
(3) Please provide the instrument parameters of the HAADF-STEM to ensure the results are perceived as reliable and convincing.(4) There are errors in the reference list, such as incomplete information for Ref. 49.

Reviewer #2 (Remarks to the Author):
The current manuscript deals with a high entropy (1 -x)BNBT-xSLTT SPE system.The manuscript reported simultaneous achievement of very high recoverable energy density (Wrec = 15.48J cm-3) with ultrahigh efficiency (η = 90.02%under a high Eb of 710 kV cm-1) by carefully engineering the local structural disorder.The obtained results are truly impressive.The volume, quality, and analysis of the experimental data presented in the manuscript are truly praiseworthy.The community will surely be benefitted from the research results presented in the current manuscript, particularly the characterization and analysis of the local structural disorder to establish the room temperature stabilization of the SPE state.While going through the manuscript I was wondering what is the novelty presented in the current manuscript.After the reporting of SPE state by Pan et al. in the 1 October 2021 issue of Science (Science 374, 100-104 (2021)) and a perspective on "The superparaelectric battery" by Y-H Chu in the same issue, various energy storage research involving SPE state with remarkable comprehensive energy storage properties have been reported in the literature.High entropy design concept to achieve enhanced energy storage properties is also not new and well reported (For e.g., L Chen et al., Nature Communications, 2022,  13:3089 for thin film and M Zhang et al., Science 384, 185-189 (2024) for a MLCC structure).So, is it about reporting and very detailed characterizations of the locally diverse structural disorder of the ferroelectric state leading to excellent comprehensive energy storage properties of a relatively newer system, (1 -x)BNBT-xSLTT?In that case taking care of the following points would certainly make this manuscript more impactful and appealing to the potential readers. 1.A rationale behind choosing this particular composition/the design strategy of the investigated system would be useful.2. How "x" in (1 -x)BNBT-xSLTT was decided, any phase field/similar simulation studies were caried out to decide on this composition (x)?If it is only based on the configurational entropy (S), is there any reason for stopping at x = 0.35?Creating local chaos in the crystal structure, both in A and B sites of the perovskite structure, has been proven fruitful in developing high entropy ceramics.Any correlation between random local field (by varying the valency and size of the dopants) in A/B site with the polar cluster size leading to the SPE state?Some discussion in this line would be useful.3. It is seen that the decrease in the polar cluster size in the RFE state is leading to the SPE state, any critical size (or its trigger, composition or temperature?) of this polar cluster that will lead to the SPE state?A discussion on this will be very helpful.4. The manuscript claims an extraordinary energy storage property of a bulk SPE composition, but the electrical performance characterizations have been carried out on samples of thickness 0.05±0.01mm, can it really be called a bulk sample?I am not sure.5. Are the sample thicknesses similar in the performance comparison of energy storage ceramics shown in figure 3  (d) and (e), if not, can they really be compared?6.Is the electrical breakdown field, Eb, reported in the manuscript is the Weibull breakdown field?If not, better to report the Weibull Eb.

Reviewer #3 (Remarks to the Author):
The capacitive energy storage is in an area of current research and interest.Recently, more and more attention is paid to both ultrahigh Wrec and η, especially for the lead-free bulk ceramics.This work demonstrates that the (1-x)BNBT-xSLTT presents a superior comprehensive energy storage performance due to the entropy engineering strategy, which disrupt long-range ferroic orders into local polymorphic distortion disorder and rich heterogeneous polarization configurations.The high-entropy superparaelectrics (SLTT-0.30)exhibits a large Wrec of 15.48 J cm-3 and an ultrahigh η of 90.02% at 710 kV cm-1.The manuscript is well written, and the findings are important to the broader ferroelectrics community.However, there are some issues to be addressed.My comments and concerns are provided as follows: 1)In terms of "High-entropy", it is a hot topic in recent.Does more element doping or solid solution mean high entropy?Can the superparaelectrics only be attributed to the highentropy systems?
2)The authors claim that the inverse relationship between Wrec and η in Introduction part.It is unclear where that comes from.Many factors are not certain to be related to the Wrec and η.The authors should give more comments.It would help reader understanding the relationship between Wrec and η.
3)It is not clear that high-entropy systems correspond to low free energy, potentially resulting in reduced barriers.Clarify in the text.4)A key challenge of this work is that SLTT-0.30 is added into BNBT to regulate configuration entropy.This solid solution content is relatively large to the ceramic.How to ensure the absence of impurities and uniform distribution of multiple elements.
5)The authors use the HR-TEM results to demonstrate the absence of the large-scale ferroelectric domain.Did the authors check the lower-magnification TEM results?More TEM images should be provided in SI. 6)Fig.2f shows the PFM image after poling treatment with ±30 V of SLTT-0.30ceramic and no domain switching was found.But why? Authors state that high-entropy may give rise to the low free energy, potentially resulting in reduced domain switching barriers.The pinning effect of defects maybe considered.Please elaborate this observation/result further.

Reviewer #4 (Remarks to the Author):
The paper reports on the fabrication of dielectric capacitors capable of simultaneously achieving high energy storage density and high charge-discharge efficiency by inducing an increase in configurational entropy in SPE states through the design of (1-x)BNBT-xSLTT composition.The authors aptly demonstrate the existence of highly dynamic PNRs in T, R, M-like phases through TEM, PFM, and Raman analysis of sintered ceramics.Furthermore, they logically correlate the superior properties of high Wrec and efficiency in the SLTT-0.30specimen with the presence of highly dynamic PNRs in various phases.Based on the excellent energy storage performance data, the paper appears to be quite well-written.However, from the perspective of this journal's requirements, the strategy of energy storage performance enhancement through entropy engineering is not entirely novel.While it's true that energy storage density and efficiency are important performance metrics for dielectric capacitors, it is now crucial to demonstrate the practical implementation of energy storage and utilization of dielectric capacitors.Therefore, I urge the authors to address and incorporate the following comments into the manuscript.

Practicality of Energy Density Values
In evaluating the energy density (Wrec) of the SLTT-0.30specimen, the authors utilized samples with very thin thickness and small electrode areas.It cannot be guaranteed that high Wrec will be maintained as the electrode area and sample thickness increase.For instance, if the sample thickness is at the level of 0.3 to 0.5 mm and the electrode diameter is at the level of 3 to 5 mm, will high Eb and Wrec be sustained?(Indeed, many papers use thicknesses and electrode areas even larger than these.)It would be beneficial to demonstrate the behavior of Eb and Wrec concerning sample thickness.
significantly lowers the switching energy barrier and makes the switching path flatter, enabling SPE behavior with ideal polarization forms.Therefore, we achieved an ultrahigh Wrec of 15.48 J cm -3 and an efficiency of over 90% in high-entropy bulk SPE.
Importantly, based on your valuable suggestions, we have made corresponding revisions to the manuscript, which have significantly improved its quality.
Comment 1: The design of local multi-phase symmetry is intriguing.Please elaborate on the advantages of this design over the common coexistence of the R and T phases in BNBT.In addition, what is the effect of distorted oxygen octahedra on energy storage performance?
Response: Thank you for your comments.We have designed the local structure of rhombohedral (R), tetragonal (T), and monoclinic (M)-like polarization configurations nested with cubic (C) phase nonpolar regions by entropy engineering.Compared with conventional two-phase coexistence, this multiple symmetry structure can further attenuate both in polarization anisotropy and switching energy barrier.Consequently, the electric field-induced polarization rotation is smoother, leading to an SPE behavior with an ideal polarization form on the macroscopic scale [Energy Environ. Sci. 16, 4511-4521 (2023)], [Appl.Phys.Lett.124, 090501 (2024)], [Science 384, 185-189 (2024)] . The local C phase is a non-polar phase, which can inhibit the polarization rotation and reduce the internal stress when loading the electric field, and promote the polarization recovery after unloading the electric field, so it can achieve the purpose of delaying polarization saturation and reducing energy loss [Adv. Mater. 36, 2313285 (2024)] .Both the R and M-like polarizations possess high polarization strengths, which are beneficial for the ceramic to achieve large polarization responses [Nano Energy 112, 108458(2023)] .Additionally, the M-like polarization has different polarization directions, which can further enhance the flexibility of the polarization configuration and lower switching barriers, thus facilitating the realization of polarization form with SPE behavior [Nano Energy 104, (2022) 107910], [Acta Mater.236, 118115 (2022)]   .
In this work, the disordered oxygen octahedra have a positive effect on the energy storage performance.Random oxygen octahedral distortions in ceramics can absorb part of the electrical energy from the applied electric field, hindering the formation of textured domain states under the electric field and thus favoring delayed polarization saturation [Nat. Commun. 13, 3089 (2022)] .Moreover, this local disorder can further disrupt longrange ordering, leading to enhanced relaxor behavior.Finally, systems with oxygen octahedral distortions typically exhibit excellent stability [InfoMat 5, 12488 (2023)] .
Comment 2: For the designed composition of (1 -x)BNBT-xSLTT, why did the authors choose SLTT as the dopant?Besides improving the entropy of the BNBT material, are there any other reasons?
2) In SLTT, SrTiO3 has a very low loss, Pr, and polarization hysteresis, which is beneficial to reduce the hysteresis loss of SLTT-x and Pr.In addition, its C phase plays a key role in delaying polarization saturation and reducing energy loss.
3) In SLTT, SrTiO3 (3.4 eV), La2O3 (5.0 ev) and Ta2O5 (4.0 eV) have a wide intrinsic bandgap (Eg), which can be adjusted to enhance the conductivity and reduce the leakage current, which is essential for improving Eb and η.
Comment 3: While in-depth exploration of the temperature stability of energy storage performance has been conducted, frequency stability is equally crucial for practical applications.Therefore, I suggest adding dielectric performance tests related to frequency in order to corroborate the frequency stability of the energy storage performance.
Response: Thank you very much for your suggestion.Frequency stability is indeed an important factor affecting practical applications.To explore this, we added frequencydependent dielectric property tests according to your suggestion.As shown in Supplementary Fig. 13, it can be observed that εr and tanδ have little dependence on frequency, which provides important support for the frequency stability of SLTT-0.30ceramics in energy storage performance.Therefore, we added this content to the manuscript and Supplementary Information: As can be observed in Supplementary Fig. 13, the εr and tanδ of SLTT-0.30ceramic fluctuate weakly with frequency, favoring the realization of frequency-insensitive energy storage performance.Supplementary Fig. 13 Frequency dependence of εr and tanδ of the SLTT-0.30.
Comment 4: For the large Eb of 710 kV/cm obtained in the SLTT-0.30sample, authors consider the high Eb is associated with entropy-induced lattice distortion, ultrafine grains (Ga), clear and dense grain boundaries, wide bandgaps (Eg), and ultralow dielectric loss (tanδ).Which factor may play a major role?Can you further explain?
Response: Thank you for your question.We believe that these factors all have an impact on Eb, and they are inextricably linked to each other.Judging by the mechanism of their impact on Eb, the lattice distortion has emerged as one of the most important factors.
The corresponding analysis is as follows: 1) Bandgap (Eg): The larger Eg means that it is difficult for electrons to transition from the valence band to the conduction band, leading to a larger intrinsic resistivity and Eb.Therefore, Eg and Eb have the following relationship with each [ACS Appl. Mater. Interfaces 13, 51218-51229 (2021)] : 2) Dielectric loss (tanδ): Low tanδ indicates reduced energy dissipation during charging and discharging, which reduces heat generation and therefore reduces the probability of thermal breakdown.
3) Grains and grain boundaries: Smaller grain sizes favor the enhancement of Eb.
On the one hand, ceramics with smaller grain sizes imply more grain boundaries.The depleted space charge layer exists at the grain boundary, which is analogous to a Schottky barrier at a semiconductor interface that can impede the migration of charge carriers [ACS Appl. Mater. Interfaces 13, 51218-51229 (2021)] .On the other hand, ceramics with smaller grain sizes have a denser internal structure with fewer voids, which can reduce harmful discharge concentrations, local failure probabilities, and dielectric losses [Chem. Eng. J. 429, 132165 (2022)], [InfoMat 5, 12488 (2023)] .
4) Lattice distortion: Lattice distortion can increase the probability of electron collisions with lattice atoms, which enhances electron scattering, leading to a decrease in conductivity and an increase in Eb [Nat. Energy 8, 956-964 (2323)] .In high-entropy ceramics, the presence of strong lattice distortion usually exhibits microstructural features of grain refinement.This is mainly due to the increase in lattice strain energy caused by lattice distortion, which hinders grain growth [Nat. Mater. 21, 1074-1080(2022)], [Science 384, 185-189 (2024)] .
Furthermore, lattice distortion can lead to solid solution hardening, and thus high entropy materials are able to withstand the compressive forces generated by the electrostatic attraction of the surface charges and stress generated by the electrostriction effect while reducing the possibility of electromechanical breakdown [InfoMat 5, 12488 (2023)], [Adv.Mater.36, 2305453 (2024)] .
It can be found that lattice distortion not only promotes Eb from a microscopic point of view but also affects grain growth, which indirectly has an effect on Eb.In addition, lattice distortion is a structural feature that can be directly observed by advanced characterization means, which provides a solid foundation for studying the relationship between structure and performance from a deeper perspective.Therefore, we think the most important factor determining Eb is lattice distortion.
Comment 5: Some minor issues: 1) The four typical vibrational modes in Raman spectra should be indicated in Supplementary Fig. 3.
2) The authors should present the configuration entropy of all the components at appropriate places to help the reader understand the relationship between SLTT and configuration entropy.
3) Please provide the instrument parameters of the HAADF-STEM to ensure the results are perceived as reliable and convincing.
4) There are errors in the reference list, such as incomplete information for Ref.

49.
Response: Thank you very much for your suggestions.We have made revisions accordingly.
1) We have labeled four typical vibrational modes in the Raman spectra.
Supplementary Fig. 5 Raman spectra of the SLTT-x ceramics.
3) We have supplemented the instrument parameters for HAADF-STEM in the Structural characterization section.The above-mentioned reports on SPE mainly focus on the study of dielectric films.
Zhang et al.'s report on high-entropy focuses on the study of multilayer ceramic capacitors (MLCCs) with a Wrec of 20.8 J cm -3 and an η of 97.5%, while the Wrec of the single-layer bulk ceramic is 10 cm -3 and η is 93.5%.The Wrec of the high-entropy bulk ceramic prepared by Chen et al. is 10.06 J cm -3 and η is 90.8%.In this work, we demonstrate that entropy engineering is an advanced approach to designing ideal bulk SPEs through advanced characterization.This design induces local ferroic distortion, which reduces the switching barrier and polarization anisotropy, and leads to excellent energy storage performance of Wrec ~ 15.48 J cm -3 and η ~ 90.02% in high-entropy bulk SPEs.Through our in-depth analysis, we believe that this can provide a valuable basis for improving energy storage performance and is worth promoting.
Comment 1: A rationale behind choosing this particular composition/the design strategy of the investigated system would be useful.
2) In SLTT, SrTiO3 has a very low loss, Pr, and polarization hysteresis, which is beneficial to reduce the hysteresis loss of SLTT-x and Pr.In addition, its C phase plays a key role in delaying polarization saturation and reducing energy loss.
3) In SLTT, SrTiO3 (3.4 eV), La2O3 (5.0 ev) and Ta2O5 (4.0 eV) have a wide intrinsic bandgap (Eg), which can be adjusted to enhance the conductivity and reduce the leakage current, which is essential for improving Eb and η.
As suggested, we have updated the rationale for choosing this particular composition/design strategy for the survey system on page 4: The sentence "Bi0.47Na0.47Ba0.06TiO3(BNBT) with high polarization genes is selected as the base material.Sr0.7La0.2Ta0.2Ti0.75O3(SLTT) is added to it to regulate configuration entropy (Sconfig) and create the (1 -x)BNBT-xSLTT system (abbreviated as SLTT-x)" on page 4 has been updated to "To ensure a large polarization response, Bi0.47Na0.47Ba0.06TiO3 (BNBT), known for its high polarization characteristics, is selected as the base material.SPEs.This phenomenon can already be well illustrated by the entropy-driven RFE to SPE transition, which fits the design core of our study.Secondly, the P-E loops in Supplementary Fig. 2 show that the P-E loops for x = 0.20 and 0.25 have large Pr and hysteresis unfavorable for energy storage.As x increases, the P-E loops become thinner, and a very thin P-E loop has been obtained at x = 0.35.We calculated the Wrec, η, and WF for x = 0.20, 0.25, 0.30, and 0.35 at 200 kV cm -1 as shown in Table R2.It can be noticed that Wrec decreases from 2.15 to 1.65 when x = 0.30 is increased to x = 0.35, while η increases only slightly from 95.11% to 95.68%, which leads to a decrease in WF from 44.17 to 38.16.From these trends, it can be hypothesized that setting x to 0.15 or 0.40 is detrimental to energy storage.Finally, from Supplementary Fig. 9, we can find that x = 0.30 possesses the densest grain distribution, the smallest Ga and the largest Eg, which are conducive to the enhancement of Eb.Based on the above discussion, increasing the SLTT content to x = 0.35 did not further improve the performance.We hypothesize that this may be due to the fact that Sconfig reaches an optimal level at x = 0.30, which is critical for improving energy storage performance.Therefore, we decided to set the SLTT content between 0.20 and 0.35.fields, which can disrupt the conventional long-range ferroelectric order into weakly coupled polar nanoscale domains (PNRs).Therefore, the random field increases with Sconfig, which leads to an increase in the content and a decrease in the size of the PNRs, which will further reduce the switching barriers, driving the RFE state evolution to the SPE state [Nat. Energy 8, 956-964 (2023)], [InfoMat 5, 12488 (2023)], [Nano-Micro Lett. 15, 65 (2023)],[Nat.Commun. 13, 3089 (2022)] . Accordingly, the introduction of chaos into the perovskite structure through a high-entropy strategy induces local random fields, which is an important factor in tuning the SPE state.To further enhance the quality of the manuscript, we have added a discussion of random fields to the manuscript.
1) The sentence "This is primarily due to the disordered component distribution leading to structural disorder, which affords infinite possibilities for tuning the polarization configuration" on page 3 has been updated to "This is primarily due to the disordered component distribution leading to unmatched atomic size, mass, valence state, and electronegativity, which induce random local strains and electric fields, providing infinite possibilities for tuning the local polarization configurations".
2) "In high-entropy systems, the introduction of foreign ions with different properties enhances the local random field, which can disrupt the long-range order into small-sized PNRs, a phenomenon that provides for lowering the switching energy barrier as well as modulating the polarization configuration in polymorphic phase coexistence systems" has been added on page 7.
3) The sentence "This phenomenon reduces the polarization anisotropy [42][43][44] , leading to the reduction of the domain switching energy barriers and thus ultimately achieving macroscopic SPE behavior" on page 8 has been updated to "The random distribution of local C-R-T-M-like phases indicates the decrease in polarization anisotropy and the existence of a strongly perturbed random field 28,[46][47][48] , which can effectively reduce the switching energy barriers and thereby lead to ideal macroscopic SPE behavior".
4) The last paragraph of page 8 has been updated as follows: "The high-entropy effect results in significant differences in atom size, mass, charge state, and electronegativity, amplifying local structure disorder and causing random local fields.
This phenomenon disrupts long-range ferroic order into locally diverse ferroic distortion with multiple BO6 tilt types and rich heterogeneous configurations.The BO6 tilt types can hinder the formation of electric field-induced long-range polarization.
Locally interconnected C-R-T-M-like phases can drastically reduce the polarization anisotropy, thereby reducing the switching barrier, resulting in a flatter switching pathway and minimizing the hysteresis loss in the SPEs.Moreover, diverse polarization configurations can also increase the polarization direction and intensity, providing a strong polarization response".
Comment 3: It is seen that the decrease in the polar cluster size in the RFE state is leading to the SPE state, any critical size (or its trigger, composition or temperature?) of this polar cluster that will lead to the SPE state?A discussion on this will be very helpful.
Response: Thank you for your suggestion.The critical size (or its trigger, composition, or temperature) that leads to the SPE state is discussed as follows: According to previous literature reports, the polar clusters of the SPE state are very small, usually a few nanometers.For size-driven SPEs, the SPE state occurs when the particle (grain or cluster) size (R) of the dielectric is in the range of Rcr < R < Rc (where Rcr and Rc are the paraelectric limit and the correlation length of polarization fluctuations, respectively).
Ideal size-driven SPEs consist of short-range-ordered nanometer polar clusters with a R of a few nanometers [Adv. Energy Mater. 10, 2001778 (2020)],[Appl.Phys. Lett. 124, 090501 (2024)] .For temperature-driven SPEs, the SPE state is when the dielectric is in the region between Tm and TB in the dielectric temperature spectrum (where Tm and TB are the temperature corresponding to the maximum dielectric constant and Burns temperature, respectively) [Ferroelectrics 76, 241-267 (1987)], [Science 374, 100-104 (2021)], [Adv. Mater. 34, 2205787 (2022)] .The main polar region in this state is only a few nanometers, which is comparable to the size of size-driven SPE particles.Therefore, the condition for obtaining the SPE state at room temperature is to reduce Tm to room temperature or below and to induce smallsized polar clusters.Our specific ratio of BNBT to SLTT has a strong influence on the formation of polar clusters.The high entropy effect (Sconfig = 1.61R) due to a high SLTT content (SLTT-0.30component) promotes the formation of smaller clusters and facilitates the desirable SPE state due to the presence of disorder and localized multiple symmetries.Current research on the energy storage performance of SPEs has focused on the temperature-driven type because it has a well-defined range of temperature boundaries (Tm to TB).Our work is based on temperature-driven SPEs, so we have added a discussion of critical temperatures on page 3: Recently, superparaelectrics (SPEs) developed in RFEs have been considered as promising candidate materials for energy storage [21][22][23] .The state of SPEs appears within the temperature range from Tm (the temperature corresponding to the maximum dielectric constant) to TB (the Burns temperature) and is characterized by weakly coupled PNRs.Therefore, SPEs not only maintain a high maximum polarization (Pm) but also allow for flexible polarization redirection with small hysteresis, leading to a higher η compared to conventional RFEs.Also, on page 5 of the manuscript, there is a description of the Tm for SLTT-0.30and SLTT-0.35:When Sconfig is increased to 1.61 (SLTT-0.30)and 1.66R (SLTT-0.35),Tm drops below room temperature, indicating that both samples have reached room temperature SPE states.
Comment 4: The manuscript claims an extraordinary energy storage property of a bulk SPE composition, but the electrical performance characterizations have been carried out on samples of thickness 0.05 ± 0.01 mm, can it really be called a bulk sample?I am not sure.

Response:
We appreciate the opportunity to clarify this aspect of our study.It can be determined that ceramics with a thickness of 0.05 ± 0.01 mm can be called bulk ceramics.We have taken care to align our terminology with that used in the broader literature; examples include Zhao et al., who described ceramics with a thickness of 0.035 mm as bulk ceramics, and similarly, Li et al., as well as Sun et al., whose reported bulk ceramics had thicknesses of 0.05-0.06mm [Nat. Commun. 14, 5725 (2023)], [Energy Environ. Sci. 16, 4511-4521 (2023)],[J.Am.Chem.Soc.146, 13467-13476 (2024)] . These results are further supported by numerous reports that consistently refer to ceramics with thicknesses in the range of 0.03-0.06mm as bulk ceramics [J. Am. Chem. Soc. 145, 19396-19404 (2023)],[J.Am. Chem. Soc. 146, 460-467 (2024)], [Small 19, 2206840 (2023)], [Mater.Horiz.11, 1732-1740 (2024)] . With respect to the established conventions within our research community, we believe our use of the term "bulk" for ceramics measuring 0.04-0.06mm in thickness is well justified.
Comment 5: Are the sample thicknesses similar in the performance comparison of energy storage ceramics shown in figure 3 (d) and (e), if not, can they really be compared?
The comparison method in Fig. 3 d and e, that is, comparing the energy storage performance at their respective Eb, is adopted by most reports.This phenomenon is also present in recently published high-level journals.This is mainly due to the limitations of the preparation process.Most sintered ceramics usually need to be mechanically thinned and polished to meet the test requirements, which makes it difficult to accurately control the thickness changes during the thinning process.The thinning and polishing process can only be stopped by personal experience to determine whether the thickness meets the test requirements, and then the thickness can be measured using precise measuring instruments.As a result, this phenomenon leads to varying thicknesses of ceramics reported in the literature, making it difficult to compare them in a uniform manner.Perhaps in the future, a suitable standard will be proposed for energy storage ceramics, which can provide a more comprehensive method to compare the energy storage performance of different systems.

Reviewer #3
Remarks to the Author: The capacitive energy storage is in an area of current research and interest.Recently, more and more attention is paid to both ultrahigh Wrec and η, especially for the lead-free bulk ceramics.This work demonstrates that the (1-x)BNBT-xSLTT presents a superior comprehensive energy storage performance due to the entropy engineering strategy, which disrupt long-range ferroic orders into local polymorphic distortion disorder and rich heterogeneous polarization configurations.
The high-entropy superparaelectrics (SLTT-0.30)exhibits a large Wrec of 15.48 J cm -3 and an ultrahigh η of 90.02% at 710 kV cm -1 .The manuscript is well written, and the findings are important to the broader ferroelectrics community.However, there are some issues to be addressed.My comments and concerns are provided as follows: Response: We are very grateful for your careful review and positive comments.In our work, we demonstrate that entropy engineering is an advanced approach to designing ideal bulk SPEs through advanced characterization.This design induces local ferroic distortion, which reduces the switching barrier and polarization anisotropy, and leads to excellent energy storage performance of Wrec ~ 15.48 J cm -3 and η ~ 90.02% in highentropy bulk SPEs.Through our in-depth analysis, we believe that this can provide a valuable basis for improving energy storage performance and is worth promoting.We have responded to each of your comments and have added relevant content to the manuscript, which has significantly improved the quality of our manuscript.
Comment 1: In terms of "High-entropy", it is a hot topic in recent.Does more element doping or solid solution mean high entropy?Can the superparaelectrics only be attributed to the high-entropy systems?
Response: Thank you very much.With more doping elements or solid solutions, the entropy gets higher.There are currently two main definitions of high-entropy: one based on components and one based on configuration entropy (Sconfig).In the former case, a high-entropy material contains more than five major metallic elements, and the molar concentration of each element is between 5% and 35% [Acta Mater. 122, 448-511 (2017)] .The latter depends on the value of Sconfig.Sconfig can be calculated using the following equation[ Nat. Energy 8, 956-964 (2023)] : where R, N (M) and xi (xj) are the ideal gas constant, atomic species and contents at the equivalent cation (anion) sites, respectively.The judgment of entropy in this work comes from the value of Sconfig.Therefore, according to the equation, the entropy increases as the number of elements increases.However, there is a special case where the entropy for a specific number of elements reaches a maximum when the number of elements is high and the atomic fractions are equal [Mater Sci Eng R Rep. 146, 100644 (2021)] .
To help readers understand the relationship between Wrec and η, we have added the following discussion in the second paragraph of the Introduction part (page 2): 1) "their η are capped at or below 80%, which is mainly caused by the AFEferroelectric (FE) phase transition".
2) "such as CaTiO3 (CT)-based and SrTiO3 (ST)-based ceramics [15][16][17][18] , the relatively low intrinsic polarization leads to their Wrec usually being lower than 7 J cm -3 .In addition, the maximum polarization (Pm) rises with the increase in electric field, thus contributing to the enhancement of Wrec.However, this process is also accompanied by an increase in remnant polarization (Pr), hysteresis loss, and leakage current, all of which have negative impacts on η 19,20 .Therefore, the trade-off between Wrec and η has become a primary challenge in designing high-performance dielectric ceramics".
Comment 3: It is not clear that high-entropy systems correspond to low free energy, potentially resulting in reduced barriers.Clarify in the text.
Response: Thank you for your suggestion.According to your reminder, after an indepth literature survey, we believe that the statement mentioned in the manuscript that high-entropy systems correspond to low free energy is not very rigorous.Therefore, after comprehensive consideration, we decided to delete this sentence, which has no impact on the overall logic and research focus of the manuscript.The thermodynamic relationship between free energy (ΔG) and entropy (ΔS) in high-entropy systems is: where ΔH is the enthalpy and T is the temperature.Based on this equation, Yang et al.
However, the effect of ΔH should not be neglected according to the thermodynamic relation equation.In some cases, if ΔS ≥ 1.5 R, this can lead to TΔS being large enough to dominate the free energy landscape and overcome ΔH [Mater Sci Eng R Rep. 146, 100644 (2021)][Prog.Mater.Sci.145, 101300 (2024)] . This is more pronounced at high temperatures.
Therefore, we believe that it is not very rigorous to say that high-entropy systems correspond to low free energy.
Comment 4: A key challenge of this work is that SLTT-0.30 is added into BNBT to regulate configuration entropy.This solid solution content is relatively large to the ceramic.How to ensure the absence of impurities and uniform distribution of multiple elements.
2) The use of high-precision weighing equipment can improve the accuracy of chemometrics.It is also necessary to prevent the loss of raw materials during the preparation process.
3) During ball milling, high-energy ball milling and increased ball milling duration can be utilized to apply sufficient energy to improve the uniformity of elemental distribution and facilitate the reaction.Moreover, the ratio of raw materials, zirconia balls and media should be set reasonably to improve ball milling efficiency.
4) A reasonable sintering temperature gradient and holding time gradient should be set.On the one hand, it can ensure the full reaction, and on the other hand, it can prevent elemental volatilization or secondary grain growth.
Finally, according to your question, we think that XRD tests should be added to describe the phase structure of SLTT-x ceramics.As shown in Supplementary Fig. 3, all components exhibit a typical perovskite structure without a secondary phase.
The coexistence of tetragonal (T) and rhombohedral (R) phases in BNBT can reduce polarization anisotropy and promote polarization rotation, thereby lowering the switching energy barrier.Meanwhile, Sr0.7La0.2Ta0.2Ti0.75O3(SLTT) is added to it to regulate configuration entropy (Sconfig) and create the (1 -x)BNBT-xSLTT system (abbreviated as SLTT-x).The high-entropy effect, combined with the small Pr, low hysteresis loss characteristics of SrTiO3 and the high bandgap (Eg) characteristics of La2O3 (5.0 eV) and Ta2O5 (4.0 eV), further enhances the energy storage performance".Comment 2: How "x" in (1 -x)BNBT-xSLTT was decided, any phase field/similar simulation studies were caried out to decide on this composition (x)?If it is only based on the configurational entropy (S), is there any reason for stopping at x = 0.35?Creating local chaos in the crystal structure, both in A and B sites of the perovskite structure, has been proven fruitful in developing high entropy ceramics.Any correlation between random local field (by varying the valency and size of the dopants) in A/B site with the polar cluster size leading to the SPE state?Some discussion in this line would be useful.Response: Thank you for your comments.Our decision on "x" was guided by configuration entropy (Sconfig) and a large amount of research data such as dielectric properties, microscopic morphology, field-induced polarization, and energy storage properties.Firstly, as shown in TableR1, the ceramics undergo a transition from lowentropy to high-entropy as well as RFE to SPE as x increases.The low-entropy x = 0 component, the medium-entropy x = 0.20 component, and the high-entropy x = 0.25 component are typical RFE states.At x = 0.30 and 0.35, both high-entropy samples are example, the NaNbO3-based ceramics prepared by Liu et al., the AgNbO3-based ceramics prepared by Liao et al., and the BaTiO3-based ceramics prepared by Sun et al.

Comment 2 :
The authors claim that the inverse relationship between Wrec and η in Introduction part.It is unclear where that comes from.Many factors are not certain to be related to the Wrec and η.The authors should give more comments.It would help reader understanding the relationship between Wrec and η.
BNT-based ceramics, such as in (1 -x)(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-xCa0.7La0.2TiO3(x taking values up to 0.43), (1 -x)Bi0.5Na0.5TiO3-xSr0.7La0.2Zr0.15Ti0.85O3(x takes values up to 0.42), (1 -x)[0.955(Bi0.5Na0.5)TiO3-0.045Ba(Al0.5Ta0.5)O3]-xCaTiO3(x takes values up to 0.4), (1x)(Bi0.47La0.03Na0.5)0.94Ba0.06TiO3-xSrTi0.875Nb0.1O3(x taking values up to 0.40), (1x)(0.75Na0.5Bi0.5TiO3-0.25SrTiO3)-xCaTi0.875Nb0.1O3(x taking values up to 0.5), (1x)(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-xCaTi0.8Hf0.2O3(x taking values up to 0.3), (1 - 4)We have checked all the references and made the following modifications to the Eb of 710 kV cm -1 ) by carefully engineering the local structural disorder.The obtained results are truly impressive.The volume, quality, and analysis of the experimental data presented in the manuscript are truly praiseworthy.The community will surely be benefitted from the research results presented in the current manuscript, particularly the characterization and analysis of the local structural disorder to establish the room temperature stabilization of the SPE state.In that case taking care of the following points would certainly make this manuscript more impactful and appealing to the potential readers.We sincerely thank you for recognizing our work and pointing out its significance and value.We are very encouraged by this.As you mentioned, our work is to use detailed characterization to prove the contribution of the locally diverse structural For the selection of SLTT, we considered its regulation of configurational entropy, its own polarization characteristics (small Pr and hysteresis loss), high bandgap, etc.Our explanation for this important innovation of combining locally diverse ferroic distortion with SPE state through entropy engineering is as follows: Indeed, both Pan et al. and Chu have significantly advanced our understanding of SPE films, while works by Chen et al. and Zhang et al. have contributed profoundly to high-entropy design research.Building upon these foundational studies, we have found a link between structural disorder caused by high entropy and the thermodynamics of the SPE state.Structural disorder due to high entropy usually disrupts the long-range ordering into small-size PNRs, which provides infinite possibilities for the emergence of diverse localized polarization configurations, especially in multiphase systems such storage performances in lead-free ferroelectrics.Nat.Commun.14, 5725 (2023).49.Zhang, Y. et al.Superior energy-storage properties in Bi0.5Na0.5TiO3-basedleadfree ceramics via simultaneously manipulating multiscale structure and fieldinduced structure transition.ACS Appl.Mater.Interfaces 14, 40043-40051 (2022).While going through the manuscript I was wondering what is the novelty presented in the current manuscript.After the reporting of SPE state by Pan et al. in the 1 October 2021 issue of Science (Science 374, 100-104 (2021)) and a perspective on "The superparaelectric battery" by Y-H Chu in the same issue, various energy storage research involving SPE state with remarkable comprehensive energy storage properties have been reported in the literature.High entropy design concept to achieve enhanced energy storage properties is also not new and well reported (For e.g., L Chen et al., Nature Communications, 2022, 13:3089 for thin film and M Zhang et al., Science 384, 185-189 (2024) for a MLCC structure).So, is it about reporting and very detailed characterizations of the locally diverse structural disorder of the ferroelectric state leading to excellent comprehensive energy storage properties of a relatively newer system, (1 -x)BNBT-xSLTT?Response: disorder to excellent comprehensive energy storage performance in the innovative SPE system (1 -x)BNBT-xSLTT.The choice of BNBT is mainly due to its high Pm and multi-phase characteristics, which can provide unlimited possibilities for improving energy storage performance.as BNBT.From a thermodynamic point of view, the design of an ideal SPE requires low domain switching energy barriers for polarization reorientation with small hysteresis.Therefore, a connection between high entropy and SPE can be expected since the switching energy barrier decreases with decreasing domain size and polarization anisotropy.Based on this, we have designed locally diverse ferroic distortions by entropy engineering, which reducing the domain size and polarization anisotropy, and inducing different BO6 tilt types.This phenomenon successfully induces an ideal SPE state with small Pr and hysteresis, large Eb, and delayed polarization saturation.

Table R1
Sconfig, ceramic properties, and dielectric state of SLTT-x.In high-entropy materials, unmatched atomic size, valence state, mass, and electronegativity can arise due to the occupation of ions with different properties in the A and B sites.This situation generates random local strain and electric of ions to induce local disorder has been shown to be very effective.And there is indeed a non-negligible correlation between random local fields and polar clusters, especially in high-entropy systems.